tools/resolve_btfids: Add --fatal_warnings option

Currently warnings emitted by resolve_btfids are buried in the build log
and are slipping into mainline frequently.

Add an option to elevate warnings to hard errors so the CI bots can catch
any new warnings.

Signed-off-by: Thomas Weißschuh <[e-mail]>
Signed-off-by: Daniel Borkmann <[e-mail]>
Acked-by: Jiri Olsa <[e-mail]>
Link: https://lore.kernel.org/bpf/[e-mail]

tools/bpf/resolve_btfids/main.c

···
 };
 
 static int verbose;
+static int warnings;
 
 static int eprintf(int level, int var, const char *fmt, ...)
 {
···
 			if (id->id) {
 				pr_info("WARN: multiple IDs found for '%s': %d, %d - using %d\n",
 					str, id->id, type_id, id->id);
+				warnings++;
 			} else {
 				id->id = type_id;
 				(*nr)--;
···
 	int i;
 
 	/* For set, set8, id->id may be 0 */
-	if (!id->id && !id->is_set && !id->is_set8)
+	if (!id->id && !id->is_set && !id->is_set8) {
 		pr_err("WARN: resolve_btfids: unresolved symbol %s\n", id->name);
+		warnings++;
+	}
 
 	for (i = 0; i < id->addr_cnt; i++) {
 		unsigned long addr = id->addr[i];
···
 		.funcs    = RB_ROOT,
 		.sets     = RB_ROOT,
 	};
+	bool fatal_warnings = false;
 	struct option btfid_options[] = {
 		OPT_INCR('v', "verbose", &verbose,
 			 "be more verbose (show errors, etc)"),
···
 			   "BTF data"),
 		OPT_STRING('b', "btf_base", &obj.base_btf_path, "file",
 			   "path of file providing base BTF"),
+		OPT_BOOLEAN(0, "fatal_warnings", &fatal_warnings,
+			    "turn warnings into errors"),
 		OPT_END()
 	};
 	int err = -1;
···
 	if (symbols_patch(&obj))
 		goto out;
 
-	err = 0;
+	if (!(fatal_warnings && warnings))
+		err = 0;
 out:
 	if (obj.efile.elf) {
 		elf_end(obj.efile.elf);